In the Admin section of VPhot you have to setup your telescope with all necessary data, except the transformation coefficients.

When upload images it is better to use the Upload wizard and you have to provide the necessary data which will be colored in red (for example the approximate coordinates of the image center and the filter you used for photometry etc.)

When you select the image after upload and plate solve, you have to load the variables either with Variable Star Index or with GCVS.

Than load the AAVSO comp stars.

Decide which variables are interested for you, decide which comparison and check stars you will use, clear the unwanted and save the sequence. You can use that sequence later for the same variable.

Be careful to not use the saturated stars. (they will be colored in gray in the left panel)

Adjust the aperture and annulus from Tool menu according FWHM (on the left) – 1.5*FWHM works well.

Read the VPhot manual and make exercises until you will be satisfied before submitting data.